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is the loop created with unmanaged switches?

Lasandro Lopez
Level 1
Level 1

i have a main switch Cisco 3650, and 2 unmanaged switches (plug and play).
i want to know, if a loop will be created if i connect like this:

1 Cable from Main Switch 3650 to Unamanged01

1 line fom unmanaged01 to unmanaged02

1 line from switch unmanaged02 to the main Switch 3650.


Will a loop created here?

is something i've to do on the main switch 3650?

Regards!

4 Replies 4

alessandro.s
Level 1
Level 1

Hi Lasandro,

Just enable Spanning-tree protocol on Cisco 3560 and you'll not create any loop.

Hope this helps.

Regards

Joseph W. Doherty
Hall of Fame
Hall of Fame

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Yes, you would create a loop.  However, as Alessandro has already noted, if STP is enabled on the 3560 it will detect the loop and block one of the ports between it and one of the unmanaged switches.

STP should be on be default, but I believe it may default to PVST.  You should enable rapid-pvst.

the STP is enabled by default, so no loops will happen, right?

Disclaimer

The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.

Posting

If STP is enabled (which I believe by default it is) on the ports that create a loop, STP will break the loop.

From what you described, if one of the links between the switches failed, STP, if necessary would unblock so all 3 switches would still be interconnected.

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